Sitecore has one of the greatest software communities that I've seen. There is a cool slack channel where you can ask and share your knowledge with the community (and also some cool memes 😂).
Also, the marketplace is where you can contribute new modules to extend the features of Sitecore so it gets better and better. What about Reddit? Yes, there is also a subreddit for Sitecore.
Moreover, the Sitecore User Groups, which are organized by members of the community, offer some effective ways to learn and do networking in the place you live. Usually, they are organized using meetups, check the upcoming user groups events in different zones of the world for the rest of the year.
Some events of the last days of 2019:
My two cents

The year 2019 was full of changes and challenges, and professional and educational opportunities appeared. Of course, I saved some time to contribute to the community as much as possible. Here are my modest contributions of the year.
Looking forward to 2020
Hopefully, in 2020, I will be adding more features to my Sitecore.Extensions module and I'll start the course about Sitecore Helix. Plus, I hope that I will do a deep dive into JSS and Cortex.
That's it for today.
Until the next post!